Warning: mysqli_real_connect(): Headers and client library minor version mismatch. Headers:50549 Library:100121 in /var/www/html/wordpress/wp-includes/wp-db.php on line 1531 July 26, 2014 - Taylor Lovett
Modifying core WordPress files is a quick way to introduce security vulnerabilities, break your site, and break future updates. From the perspective of a developer, nothing is worse than searching through a theme and plugins for a problem only to discover a previous developer modified a core WordPress file an introduced a bug.
I wrote a simple Node module that lets you easily check WordPress installations for modified or removed core files. Install the detect-wp-core-modifications npm package with the following shell command: